This invention relates to the field of air pollution control and, more particularly, to an improved apparatus and method for controlling the emissions caused by the pushing of coke from coke ovens.
The discharge of coke from a coke oven presents an exceptionally difficult and offensive air pollution problem. When the coke at a temperature of .about. 2,000.degree.F. is suddenly discharged from the oven into the waiting quench car, there is a massive release of heat to the surroudings. This heat release causes an emission in the form of a rapid and voluminous updraft containing significant amounts of particulates picked up from the coke. Subsequent fallout of these particulates from the emission scatters solid pollutants over neighboring areas extending a substantial distance from the coke oven battery. The emission also includes noxious gases emanating in part from discharge of the oven and formed in part by partial combustion at the surface of the glowing coke between carbon of the coke and oxygen from the surrounding air. These noxious gases may present a hazard to the workmen positioned on the discharge side of the oven.
Various devices have been proposed in the art for the control of the emission produced upon the pushing of coke from a coke oven. Most of these devices have included traveling hoods adapted to be positioned over either the coke guide or the quench car. Such a hood has typically been provided with a blower for removal of gases therefrom and a scrubber or other means for separation of the particulates from the gases. The effectiveness of such emission control systems has been very limited since the volume of the hood is generally inadequate to contain the rapid flow surge which is produced as the oven is pushed. As a consequence, a substantial portion of the gases and particulates tend to escape and pollute the surrounding area. Given the limited volumetric capacity of these traveling hoods, such problems could be overcome only by providing an exceptionally high capacity exhaust system for the hood. This factor, together with the high energy scrubbing system needed to remove the high particulate load in the gases exhausted from the hood, requires a very high power consumption, for example, on the order of 2,000-3,000 hp. Where a traveling hood has been designed and adapted to cover areas within which workmen may be stationed, moreover, the hood tends to confine and concentrate noxious gases, presenting a serious hazard to the workmen. Because of their size, weight and mechanical complexity and the severe environment in which they are used, traveling hoods are not only expensive to install, but are also subject to potentially serious maintenance problems with attendant downtime and repair expense.
Many of the serious problems encountered with traveling hoods have been resolved by the stationary emission control shed described in Roe and Patton U.S. Pat. No. 3,844,901. In this system, a peaked roof shed extending along the length of the coke side of the battery includes an entrapment zone adjacent the oven discharge doors, a throat above the entrapment zone for acceleration of the gases, an expansion and collection chamber above the throat where some of the particulates are deposited and collected, and an exhaust duct in the apex of the peaked roof for removal of the gases from the shed. In the collection chamber, the gas flow reaches the underside of the peaked roof and is then turned down to cause recirculation and cooling of gases directly above shelflike portions extending outwardly from either side of the throat. Particulates separate from the gases and fall out on the surfaces of these shelflike portions.
Although the system described in the aforesaid patent is substantially superior to those systems previously known, it does not prevent fallout, often appreciable, of particulates back into the coke car track area. As the particulates separate from the gases in the collection chamber, they are falling back in the direction of the entrapment chamber. Not all of these particulates collect on the shelves on either side of the throat, and those which do not collect on the shelves normally find their way back onto the tracks or the working area on the coke side of the battery. A problem is also presented by the accumulation of solids on the shelflike areas on either side of the throat. This accumulation must be periodically removed, and the removal process is normally a dirty and potentially hazardous manual operation. Despite the material improvement in coke oven emission control afforded by the process of U.S. Pat. No. 3,844,901, therefore, a further need has existed for improved emission control systems which substantially eliminate fallout of particulates in the track or working areas, and which provide positive collection and removal of solid particulates from the system.